IN an opinion piece entitled ‘Our hot, dry future’ published by Melbourne’s The Age newspaper on October 6, 2008, Dr David Jones, head of climate analysis at the Australian Bureau of Meteorology, suggested global warming was responsible for the current long drought in Melbourne and that there was worse to come.
I don’t think the article was very convincing. I am annoyed that it didn’t include any real data. While Dr Jones claimed that “We know that over the past 11 years Melbourne's rainfall has been about 20% below the long-term average”, he didn’t explain what period this “long-term average” covers and what is the relevance of the last 11 years given it is accepted that over this period there has been a dominance of El Nino, and therefore dry conditions.
Key Australian Institutions have claimed for some time that we have a water crisis because of climate change.
Indeed in 2005 CSIRO published a "Melbourne Water Climate Change Study" claiming "...the greater Melbourne Region has had its lowest rainfall on record compared to all other periods of similar length.”
But as blogger, Warwick Hughes, showed some time ago, the period chosen was just 92 months, from October 1996 to May 2004.
In order to put their statement in some context Mr Hughes graphed high quality rainfall data for the weather station closest to Melbourne, Yan Yean, back to January 1863 – and he has just updated the chart to the end of September 2008.
A high quality version of this chart can be found at Mr Hughes' website, click here.
The chart indicates that Melbourne experiences dry periods every so often and that the current drought is similar in magnitude to the droughts of 1896, 1925 and 1945. The chart showing 145 years of data, does not support the claim, made by Dr Jones in his article in Melbourne’s The Age, that there has been recent unusual climate change in Melbourne. Indeed periods of drought and flood are a natural hazard.
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Read Part 1 here:
https://climatelab.com.au/blog/2008/10/how-melbourne%e2%80%99s-climate-has-changed-a-reply-to-dr-david-jones-part-2/
Read Part 2 here:
https://climatelab.com.au/blog/2008/10/how-melbourne%e2%80%99s-climate-has-changed-a-reply-to-dr-david-jones-part-1/
Hey Warwick, i got your email, but I can't get an email out from my system to you - i'm still travelling - so am posting this message here - your comment is not in spam. Try posting again. Cheers,
Why guess when you're being informed on a very good story as to why the rainfall is missing the continent ! You could try to read what's been done . The rainfall decline in SWEA is a response to the intensification of the Sub-Tropical Ridge and appears linked to global warming.
[...] has experienced declining rainfall over the past 11 years. In response, Dr Jennifer Marohasy posted ‘How Melbourne’s Climate Has Changed: A reply to Dr David Jones (Part 3)’, which included a graph of high quality data of rainfall at Yan Yean, Victoria, because of its [...]
I see what he's done now. If I'd graphed it I would have had the moving average finishing at the end of the graph, but he's moved it back so that the peaks and troughs coincide with troughs and peaks in the actuals. Fair enough.
Mr. Graham Young:
How could the 92 month smoothing "go to the end of the graph." If it did that, at the end of the graph it would have to include data from half the 92 month smoothing interval, or 46 months, from the future.
There actually looks to be a problem with the graph. If the 92 month "smooth" is a rolling average, then it ought to go to the end of the graph in which case my eye tells me that it will be lower than at any other time in the period.
I'd disagree with Luke that this is the wrong statistical technique to use (subject to the blog post Jen has after this referencing Franks). It would have been better to have a number of sites represented, but I'm not sure that anyone has shown this site to be unrepresentative.
The same David Jones gave a climate change presentation on behalf of the BOM to a farmers expo in western Victoria in july this year.
Up there on the screen as a prime exhibit was the now completely discredited Mann hockey stick as a prime example of how global temperatures are rising and will continue to rise.
An audience comment on the levelling off of global temperature rises over the last ten years and the ARGO data on on the lack of increases in deep ocean temperatures were sarcastically dismissed as "nonsense".
In David Jones, you are dealing with one of the more extreme global warming ideologists and believers who have made it their mission to use their BOM status to push their ideology at every available opportunity.
In doing so he is causing a good deal of harm to the status and reputation of the BOM which may come back to haunt them in the years ahead.
Well "guesses" of course are highly scientific - but to the point of seasonality.
http://www.agu.org/pubs/crossref/2008/2008GL033727.shtml
The rainfall decline in SWEA is a response to the intensification of the Sub-Tropical Ridge and appears linked to global warming.
http://www.mdbc.gov.au/subs/seaci/docs/ASM2008/ASM08_M112_131_141_Timbal.pdf
Timbal, B., Wheeler, M. and Hope, P. (2008) On the relationship of the rainfall in the southwest and southeast of Australia. Part II: Possible causes of recent declines. submitted Journal of Climate.
This analysis is all but useless since it does not take the seasonal rainfall into account. Show me the trends for summer, winter, spring, & autumn. Of course the lack of rainfall seems to correspond to global cooling rather than warming so there are plenty of other arguments about the cause of our drought not being AGW. My guess is that its caused by natural climate change 🙂